LCD20x4

Connects over

I²C

Address

0x27 (or 0x20, 0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x3F, 0x38, 0x39, 0x3A, 0x3B, 0x3C, 0x3D, 0x3E)

Made by

Generic (HD44780 + PCF8574 backpack)

Datasheet

sparkfun.com

Use it

hardware {
    device lcd20x4: LCD20x4
}

every 1s {
    lcd20x4.clear()
}

On its own, the declaration puts the LCD20x4 on the first I²C bus (SDA 21, SCL 22 on the ESP32) at 0x27. To choose the pins or the address, declare the bus and attach the device: device lcd20x4: LCD20x4 on i2c0 at 0x20 with i2c i2c0(sda: 21, scl: 22).

Methods

• lcd20x4.clear()

  Clear the display

• lcd20x4.print(text: string)

  Print text at cursor

• lcd20x4.set_cursor(col: int, row: int)

  Move cursor (col 0-19, row 0-3)

• lcd20x4.backlight(on: int)

  Toggle backlight on/off

• lcd20x4.create_char(slot: int, r0: int, r1: int, r2: int, r3: int, r4: int, r5: int, r6: int, r7: int)

  Define custom character 0-7 from 8 rows of 5-bit pixels (top to bottom)

• lcd20x4.write_char(code: int)

  Write a raw character code at the cursor (0-7 = custom chars)

• lcd20x4.reinit()

  Re-initialise the display (recovers garbled characters after noise or a supply dip); redraw afterwards

Wiring

Specifications

Voltage

5V

Current

1.5 mA + ~30 mA backlight

Characters

20 columns × 4 rows

Interface speed

I²C up to 100 kHz

Tips

• Line addressing isn't sequential — line 3 starts at column 0x00+0x14, line 4 at 0x40+0x14. Most drivers hide this.
• Drawing 80 chars over I²C at 100 kHz takes ~50 ms — avoid refreshing the whole screen every frame.

Alternatives worth knowing:

• SSD1306: OLED — smaller package but you get graphics.
• ST7789: Color TFT — more pixels, more flexibility, more code.